@christophebler Ok, than the serial line works well. But I still recommend using our opensource image because the parameters that can be set using the github version is limited and might cause some troubles which are fixed in the opensource image.

Byt the way, what do you want to do by 'Set Adress to 0 and rebooted both devices'? You can set address only at the slave which is the xS50 and if you set it to 0, than the SW configuration is used (address 15, 19200bps, no parity) and you are opening different device...

Address 0 is not allowed on Modbus, thus the behavior like I described.